package com.papper.mng.utils.tool;

import org.apache.commons.codec.binary.Base32;
import org.apache.commons.codec.binary.Base64;

import javax.crypto.Mac;
import javax.crypto.spec.SecretKeySpec;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;

/**
 * GoogleAuthenticator
 * <h5>描述:</h5>
 */
public class GoogleAuthenticator {
    public static final int    SECRET_SIZE             = 10;
    public static final String SEED                    = "g8GjEvTbW5oVSV7avLBdwIHqGlUYNzKFI7izOF8GwLDVKs2m0QN7vxRs2im5MDaNCWGmcD2rvcZx";
    public static final String RANDOM_NUMBER_ALGORITHM = "SHA1PRNG";
    int window_size = 3;

    public void setWindowSize(int s) {
        if (s >= 1 && s <= 17) {
            window_size = s;
        }
    }

    public static Boolean authcode(String codes, String savedSecret) {
        long                code = Long.parseLong(codes);
        long                t    = System.currentTimeMillis();
        GoogleAuthenticator ga   = new GoogleAuthenticator();
        ga.setWindowSize(15);
        boolean r = ga.check_code(savedSecret, code, t);
        return r;
    }

    public static String genSecret() {
        String secret = GoogleAuthenticator.generateSecretKey();
        return secret;
    }

    public static String generateSecretKey() {
        SecureRandom sr = null;
        try {
            sr = SecureRandom.getInstance(RANDOM_NUMBER_ALGORITHM);
            sr.setSeed(Base64.decodeBase64(SEED));
            byte[] buffer      = sr.generateSeed(SECRET_SIZE);
            Base32 codec       = new Base32();
            byte[] bEncodedKey = codec.encode(buffer);
            String encodedKey  = new String(bEncodedKey);
            return encodedKey;
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        }
        return null;
    }

    public static String getQRBarcodeURL(String user, String host, String secret) {
        StringBuffer qr = new StringBuffer();
        qr.append("otpauth://totp/").append(user).append("@").append(host).append("?secret=").append(secret);
        return qr.toString();
    }

    public boolean check_code(String secret, long code, long timeMsec) {
        Base32 codec      = new Base32();
        byte[] decodedKey = codec.decode(secret);
        long   t          = (timeMsec / 1000L) / 30L;
        for (int i = -window_size; i <= window_size; ++i) {
            long hash;
            try {
                hash = verify_code(decodedKey, t + i);
            } catch (Exception e) {
                e.printStackTrace();
                throw new RuntimeException(e.getMessage());
            }
            if (hash == code) {
                return true;
            }
        }
        return false;
    }

    private static int verify_code(byte[] key, long t) throws NoSuchAlgorithmException, InvalidKeyException {
        byte[] data  = new byte[8];
        long   value = t;
        for (int i = 8; i-- > 0; value >>>= 8) {
            data[i] = (byte) value;
        }
        SecretKeySpec signKey = new SecretKeySpec(key, "HmacSHA1");
        Mac           mac     = Mac.getInstance("HmacSHA1");
        mac.init(signKey);
        byte[] hash          = mac.doFinal(data);
        int    offset        = hash[20 - 1] & 0xF;
        long   truncatedHash = 0;
        for (int i = 0; i < 4; ++i) {
            truncatedHash <<= 8;
            truncatedHash |= (hash[offset + i] & 0xFF);
        }
        truncatedHash &= 0x7FFFFFFF;
        truncatedHash %= 1000000;
        return (int) truncatedHash;
    }
}
